In joint arthroplasty, regardless of the joint, there are several types of prostheses that differ depending on the pathology to be treated, the health status of the patient, and the type of route and operating technique.
Surgeons wish to adapt the preparation of a bone intramedullary canal as a function of the type of prosthesis that they wish to insert, in order to assure an efficacious and risk-free operation, while guaranteeing the reliability of the implant anchoring.
Medullary sizing is done by means of a reamer. This reamer shapes the intramedullary canal with precision so that the volume obtained corresponds to the volume of the implant to be positioned. For this, the reamer is covered partially or completely with teeth over its outer envelope, and these teeth cut and tamp spongy and cortical bone.
There are different types of teeth, more or less aggressive, which permit the medullary sizing desired by the surgeon, as a function of the type of prosthesis chosen. For these different types of teeth, it is possible to vary the parameters of the teeth: cutting angle, top flat part of the tooth, pitch, orientation of the teeth.
A reamer in the shape of a hollow shaft provided with teeth on its surface is known from patent EP 0 634,145. The reamer comprises a longitudinal slit that gives elasticity to the reamer. One disadvantage of this reamer is that the stresses are concentrated at the bottom of the teeth during reaming of the bone, entailing significant risks of breaking.
This problem is resolved in patent EP 0 563,585 and patent application EP 1,174,201 by helical teeth permitting the stresses to be distributed over the helix formed by the teeth.
Patent EP 0 563,585 discloses a plastic reamer provided with helical teeth with different angles of attack along the reamer, the teeth possibly being divided into two parts along the cutting edge of the reamer. The reamer comprises an inner canal that permits aspiration of bone debris during reaming.
Patent application EP 1,174,201 teaches a reamer provided with teeth positioned in a helix, which is machined into the surface of the reamer body.
One disadvantage of all these reamers is that they are difficult to manufacture, and therefore used for several patients, being cleaned and sterilized between every two patients. However, cleaning reamers is difficult due to the angular shape of the teeth, and in particular the retention zones that make up the teeth, which can lead to a contamination of bone or marrow from one patient to another and therefore to transmission of Kreuzfeld-Jacob-type diseases.